Permanently crimped textile materials of increased elasticity



United States Patent O PERMANENTLY CRIMPED TEXTILE MATERIALS OF INCREASED ELASTICITY Charles H. Fisher, New Orleans, La., assignor to the United States of America as represented by the Secretary of Agriculture No Drawing. Original application June 21, 1962, Ser. No. 204,299. Divided and this application May 27, 1966, Ser. No. 554,638

3 Claims. (Cl. 28-76) ABSTRACT OF THE DISCLOSURE A process for producin fibrous cotton textile yarns and fabrics that exhibit stretch and recovery characteristics. The fibrous cotton starting material is chemically modified to a quite specific minimum degree, which specific degree depends upon the particular chemical modification chosen, for the purpose of obtaining a fibrous thermoplastic cotton. The chemically modified fibrous cotton material is then heated until it becomes thermoplastic, whereupon it is mechanically shortened so that linear portions of the thermoplastic material is either yarn or in sheet form are displaced into different planes. The shortened material, when cooled below the temperature of thermoplasticity, exhibits elastic properties.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This appliction is a division of Ser. No. 204,299, filed June 21, 1962, now abandoned.

It is known to produce elastic textile yarns by highly twisting normally twisted or untwisted yarns, subjecting them in such condition to heat fixation and detwisting them back to the original degree of twist. This method has achieved great importance principally in connection with the use of endless filaments of fully synthetic material such as polyamides or polyesters, an elastic yarn being obtained which has achieved great importance principally for socks and stockings, but also generally for knitted articles and lately also in weaving. It is known that not all persons tolerate direct contact with the skin of wearing apparel made of fully synthetic material, and therefore there is a need for elastic yarns made of other materials.

Cellulose fibers would make an ideal material for such purposes. However, the lack of sufiicient thermoplasticity and the necessity of spinning short fibers to obtain the yarn have heretofore presented insurmountable difficulties.

It has now been found that textile yarns of increased elasticity can be obtained from cellulose yarn, particularly cotton yarn, which has been rendered thermoplastic and then mechanically deformed. These elastic yarns exhibit very favorable textile properties.

One object of the invention, therefore, is to provide a method for producing textile yarns to which an increased thermoplasticity has been imparted by chemical modification. Another object is to produce from such yarns, cellulosic yarns of increased elasticity.

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As is known, ordinary cotton yarns are thermoplastic only to a very limited extent, so that it has hitherto been impossible to permanently deform cotton yarns by the methods applicable to synthetic monofilament yarns.

In accordance with the present invention, it has been found that the thermoplasticity of cotton may be increased by chemical modification, for example, by acetylation, cyanoethylation or benzylation. It was surprising to those skilled in the art that by merely a slight esterification or etherification it is possible to so greatly increase the thermoplasticity of spun cellulose yarns that, after treatments heretofore applicable only to synthetic yarns, the fibrils show a plastic deformation and interior torsional tensions which are decisive for obtaining permanent elasticity. Ordinary cotton yarns shown no modification of their physical properties worth mentioning, when subjected to such a treatment.

Methods for mechanically manipulating thermoplastic fibers, yarns, and woven textiles to achieve therein elasticlike stretch properties are well known in the art. Force applied longitudinally to the opposite ends of a length of fiber, yarn or fabric, will effect a folding or a bending of the material and hence a longitudinal shortening. When these folds or undulations are set in a thermoplastic material, the net result besides a shortening of the material is a denser and a fuller material possessed of a certain amount of stretch or elasticity by virtue of the set folds or bends. In the case of fibers or yarns, the application of rotational force to induce twisting of the fiber or the yarn will produce, when the twist is set, stretch or elastic properties by virtue of a physical shortening of the fiber or yarn in the longitudinal direction. The method or device employed to achieve the physical shortening requisite for inducing stretch properties is not particularly important. The situation being simply that once a chemically modified cotton fiber, yarn, or fabric that possesses the requisite thermoplastic character has been prepared, the manipulations required to bring about stretch properties in the material can be accomplished by a variety of mechanical means all well known in the art.

Shortening of the yarn by a twisting operation is one of the preferred physical treating methods for the production of yarns for knitting. Such a procedure is described and claimed in the copending application of Ernest Weiss, Ser. No. 204,079, filed June 21, 1962.

Other procedures are applicable, as will be shown in examples below.

In accordance with one aspect of the invention, it has been found that, by chemically modifying cotton fibers as described below, it is possible to obtain yarns that are especially suitable for mechanical manipulation while thermoplastic. Particularly suitable are acetylated cotton yarns whose degree of substitution is at least 1, cyanoethylated cotton yarns whose degree of substitution is at least 0.4, and benzylated cotton yarns whose degree of substitution is at least 0.2. The term degree of substitution means the number of OH groups per unit of glucose which have been esterified or etherified. The degree of substitution in the case of any of the chemical modifications may be carried to the point at which fibrous character of the roving or the yarn is lost. It is possible, for example, by the use of low temperature esterification and the exercise of extreme care to acetylate cotton cellulose to a degree of substitution of 3.0 with retention of fibrous character. Such high substituted yarns or roving are operable for the purpose of this invention, as long as fibrous character of the cellulose is retained after chemical modification.

Modified cotton yarns of this type can be obtained, for example, in the following manner:

Example 1.Acetylation procedure (higher acetyl) used to acetylate Pima S-l roving in 6 pound package dyeing machine.

Approximately 1% pound of 1.5 hank roving was processed on each of 3 special stanless steel dye tubes. (Two 1 /8" x 6 /4 dye tubes cut off to lengths of 5%" and then butt welded to form a tube 1%" in diameter x 10" long.) The 3 packages were put in the package dyeing machine and presoaked 17 hours (overnight) in 99% acetic acid -1% water. The presoaking solution was drained and the reaction was carried out in a 54.75% acetic anhydride, 45% isopropyl acetate, 0.25% perchloric acid solution. Reaction time: 2 hour, 45 minutes. Reaction temperature C. Acetyl content 35.8%.

The roving was redrafted into roving suitable for spinning 40s yarns.

Example 2.Acetylation procedure (lower acetyl) Presoak2 hours 60C. in glacial acetic acid.

Drain and then react for 1 /2 hours in acetic anyhydride 74.85% acetic acid, 0.15% perchloric acid at 20 C. Expected acetyl content 23-28% on roving.

Drain, wash in tap water, and then increase water temperature to 90 C. for final wash.

Example 3.Cyanoethylation procedure Wet out yarn thoroughly in 2% by weight exact sodium hydroxide solution in package dyeing machine. Remove yarn, centrifuge packages to approximately 70% wet take-up. Replace yarn in package machine, and react in water-saturated acrylonitrile at 60 C. for to 45 minutes. Drain and blow with air. Expected nitrogen content 4-5%. Drain and wash thoroughly in phosphoric acid 1% solution. Drain, wash in tap water until all reagents are removed.

Example 4.Benzylation procedure The yarn (A pound) was wound on a 1%" stainless steel perforated dye tube with extremely light tension making a very soft package. It was then saturated with aqueous caustic soda solution (30% NaOH, 1% ethylene glycol by wt.) in the package dye machine, with the solution being pumped from the inside to the outside of the package for approximately 30 minutes at about 30 C. The solution was drained off and the package extracted in the machine by blowing air through it from the inside-out direction. The reaction is then carried out by filling the machine with pure benzyl chloride and heating to 95100 C. while circulating the solution.

Optimum reaction is the point when the flow rate from inside-out, which will increase steadily to a maximum then decrease steadily, reaches the same value that was obtained when starting the reaction. The solution is then cooled to about room temperature, drained out and the package again extracted with air and then washed with hot water (60 C.) for approximately 30 minutes, then with a synthetic detergent for approximately 30 minutes and finally with hot water.

Yarns are used which have a low degree of spinning twist corresponding to a twist constant a of maximum 4, preferably 2-3. The twist constant at is calculated in accordance with the formula 0:: T/ /Ne, T being the number of turns per English inch and Ne the English yarn number.

The yarns prepared in accordance with this invention are relatively voluminous and elastic, their elasticity, expressed in percent in accordance with the formula is preferably 10%-30% or more, a being the length of a strand of the yarn wetted with water and b being the length of the same strand after it has been dried in unstressed condition and then measured while subjected to a stress of 0.018 g./tex. [Tex is the new international number system for all of textile yarns; tex=gram per 1000 meters] The yarns further have a beautiful and full silky feel and have a better covering capacity than conventional cotton yarns. They have a relatively great absorption capacity and thus have advantageous physiological properties.

Details of the production of twisted elastic yarns from the above described acetylated, benzylated, and cyanoethylated cotton are given in the previously mentioned application of Ernst Weiss, Ser. No. 204,079, filed June 21, 1962.

In addition to the procedures described in the copending application, it is possible to use other methods to produce elastic yarns of different physical structure. One such method is given in the following example.

Example 5 A sample of partially acetylated cotton yarn (SO/2) of acetyl value 26% was shortened by mechanical means at a temperature of 200 C. and then set in the presence of saturated steam at 144 C. In this particular case, the mechanical manipulation involved, in etfect, the application of force against the opposite ends of the yarn, the force being applied on incremental segments of the yarn in a lengthwise direction. The acetylated yarn and mechanically manipulated yarn exhibited an elongation of 14.2%.

A mechanical shortening can also be applied to fabric that has been chemically modified, as shown below.

Example 6 A sample of x 80 chemically modified cotton print cloth (acetyl value approximately 20%) was shortened 5% in the warp direction and approximately the same amount in the fill direction with heating. The mechanically shortened fabric exhibited 25% elongation in the warp direction and 21% elongation in the till direction after treatment.

Example 7 Table I shows stretch yarns prepared from acetylated cotton yarns by heating the chemically modified yarns to the temperature at which they become thermoplastic and then shortening by mechanical means the heated thermoplastic yarns.

TABLE I.COTTON STRETCH YARN 1 Sample Preheat tempera Elongation,

ture, F. Percent 1 Yarn (50/2)26% acetyl mechanically shortened while thermoplastic.

Example 8 TABLE IL-COTTON STRETCH FABRIC l Shortening ot Tearing strength Heat test fabric as a Breaking strength Flex abrasion (stoll) (trapezoid) percent (160 0.), per- Elongation result of percent olpercent ofoicent breaking at break mechanical strength aftermanipulation W. F. Control Retained Control Retained Control Retained 1 day 7 days W. F.

W. F. W. F. W. F. Sample (80 x 80 print cloth):

Control 100 100 100 100 100 100 56 22 8 21 Acetylated and shortened 86 97 82 76 95 93 98 83 17 22 Sample (Osnaburg Control 100 100 100 100 100 100 38 20 i3 22 Acetylated and shortened 5. 0 4. 5 72 86 47 102 72 76 108 100 19 19 Sample (48 x 48 sheeting):

Control 100 100 100 100 100 100 56 22 12 21 Acetylated and shortened 6. 0 6. 0 89 99 19 20 68 73 105 91 13 26 1 Fabric acetylated to 20% acetyl, heated and shortened while thermoplastic.

I claim:

1. A method for producing a permanently elastic cellulosic material of the group consisting of thermoplastic chemically modified cotton yearns and fabrics, said chemically modified cotton being a member of the group consisting of (1) cotton acetylated to a degree of substitution of at least 1.0, but insufficient to destroy its fibrous character, (2) cotton benzylated to a degree of substitution of at least 0.2 but insufficient to destroy its fibrous character, and (3) cotton cyanoethylated to a degree of sub- 30 stitution of at least 0.4 but insufiicient to destroy its fibrous character, said method comprising:

(a) heating a member of the above defined group chemically modified cellulosic material until it becomes thermoplastic;

(b) applying a longitudinal force to opposite ends of a length of said heated cellulosic material to effect a References Cited UNITED STATES PATENTS 1,451,331 4/ 1923 Dreyfus. 2,980,491 4/1961 Segal et al. 8120 2,990,234 6/1961 Klein et a1. 8120 JOHN PETRAKES, Primary Examiner. 

